Sucrose can be substituted by intense sweeteners to lower the calorie content of soft drinks. Although the sweetness is kept at the same level as much as possible, the flavour of the product often changes. This change could be due to both the mechanism of sensory perception and interactive effects of the aroma compounds. Several types of interaction and some techniques for measuring interactive effects are reviewed. An example of psychological interaction is the influence of colour on flavour. Interactions of flavour molecules with the receptor can be affected by changes in their micro-environment. Molecular interactions play a role in the release of volatile compounds from aqueous solutions; release is increased by sugars and salts, and decreased by lipids and proteins. Intense sweeteners, such as aspartame and neohesperidine dihydrochalcone, interact with volatile compounds and modify the intensities of flavour attributes. The use of combinations of intense sweeteners can solve the flavour problems encountered with single sweetener applications. A quaternary model of Beidler's mixture equation was used to describe the sweetness of a light blackcurrant soft drink, containing the intense sweeteners saccharin, cyclamate, aspartame and acesulfam-K. The perceived sweetness of the light soft drink was lower than the sweetness of the original sucrose-sweetened soft drink. A proportional enhancement of the concentrations of the intense sweeteners was utilized to meet the sweetness of this classic soft drink. Consequently, the aroma attribute strawberry increased, while the currant and sour related attributes decreased.